Recently dry laundry detergents have been developed which contain enzymes which are highly effective not only against proteinaceous soils, such as blood, gravy and the like, but are also effective against carbohydraceous and fatty soils. In some cases enzymes have been added to dry detergent compositions to be used as a presoak prior to washing, while in other cases the enzymes have been added to the dry washing composition itself. With an enzyme-containing detergent composition it is a necessary requirement that the enzyme remain stable for extended periods of time of at least up to 12 months at ordinary temperatures. Because of this requirement of stability, enzymes in the past have only been incorporated with dry detergent compositions. In liquid or aqueous compositions, enzymes have a tendency to deactivate either through reversible inactivation or through irreversible activation in which chemical changes occur in the enzyme structure to prevent further activity.
The inherent instability of enzymes in liquid detergent solutions is due to several factors, first an aqueous phase in itself is a hostile environment for the enzymes, and while stabilized aqueous enzyme solutions have been prepared in the past, these stabilized solutions have had an acidic or neutral pH and not a highly alkaline pH as in an aeuqous detergent solution. Further, the surfactants, detergent builders and chelating agents commonly used in detergent or laundry compositions are hostile to the enzyme in that they tend to be toxic to the enzyme protein. For these reasons, enzymes have been used exclusively with dry detergent compositions in the past.